In an internal combustion engine for a vehicle, the combustion energy includes kinetic energy and heat energy. This heat energy is utilized for controlling a temperature in a vehicle interior. Engine waste heat is used to warm the air of the vehicle interior.
JP-U-61-186766A and JP-11-324746A describe an ignition timing of a spark plug and valve timings of intake/exhaust valves are controlled to increase the engine waste heat quantity.
When increasing the engine waste heat quantity based on the heat-utility requirement, a fuel consumption depends on an engine driving condition. However, in the apparatus disclosed in the above patent documents, the ignition timing and the valve timings are controlled without respect to the engine driving condition. Thus, it may excessively increase the fuel consumption and may cause a deterioration in fuel economy.
In order to improve fuel economy, a hybrid vehicle and an idle reduction control system have been developed.
Generally a waste heat of an engine is utilized for heating an interior of a vehicle through engine coolant. However, if the engine waste heat runs shortage, it is likely that enough heat quantity is not ensured for heating the interior of the vehicle.
Japanese Patent No. 3704788 shows a heating system which includes a heating device utilizing the engine waste heat and a heat pump device driven by an electric motor.
This heating system is provided with a plurality of heat sources which are used for heating the interior of the vehicle. However, the above Japanese patent does not show how much energy is used from which heat source in view of effective utilization of heat energy.
JP-2006-166639A (US-2006-122737A1) shows an electric-power-source controller computing a fuel quantity which each electric-power source consumes for generating a unit electric-power. This fuel quantity is referred to as an electricity-fuel rate. The controller determines a combination of the electric-power source in such a manner that the electricity-fuel rate becomes a minimum value. The electric-power source includes a generator, a battery, and a generator utilizing engine waste heat.
In this control system, the electricity-fuel rate of the generator is varied with respect to a total supplied electric power, and the electricity-fuel rates of the battery and another generator are constant values. Based on the variation in the electricity-fuel rate of the generator, an allocation of electric power of each electric-power source is determined.
However, in a case that the electricity-fuel rates of multiple electric-power sources are varies, it is not always easy to determine the load allocation of each electric-power source in such a manner that the total electricity-fuel rate becomes a minimum value. If all combination of the electric-power sources is computed to determine an optimum allocation, a computation load may be exponentially increased.